Academy Award-winning screenwriter William Goldman ("Butch Cassidy and the Sundance Kid," "Marathon Man") says there is a key rule that you must always remember to understand the way things work in Hollywood: "Nobody knows anything."

In the days leading up to the 2012 NFL Draft, former Super Bowl-winning head coach Brian Billick examined the one thing that confounds even the most advanced NFL minds -- drafting a quarterback.

When it comes to pro football, the same phrase applies to the complex, tortured exercise of deciding who can and can't play quarterback. There's something of an art to it, but all attempts at science have failed.

In the late 1960s at the dawn of the Super Bowl era, teams succeeded only about 50 percent of the time in identifying quarterbacks taken in the first 10 selections of the draft, where each pick carries All-Pro expectations. Overall, in the entire first round -- where you at least want a long-time quality starter -- their collective record on QBs was identical: about 50 percent. Sometimes teams were right (like when the Pittsburgh Steelers took Terry Bradshaw with the first pick in the 1970 draft) and sometimes they were flat wrong (like when the Chargers took Marty Domres with the ninth pick in the 1969 draft). Sometimes teams made selections that, in retrospect, seem implausible. In 1967, with the third pick in the draft, the San Francisco 49ers chose Heisman Trophy winner Steve Spurrier from Florida. One pick later, the Miami Dolphins took future Hall of Famer Bob Griese.

Today, with the benefit of decades more experience, a keener understanding of the qualities needed to be successful and millions of dollars spent in scouting and evaluating talent with precision ... teams still are hitting about 50 percent in trying to identify future All-Pro quarterbacks in the first 10 picks, and the same 50 percent with first-rounders in general.

There are two ineluctable truths that one can never forget about the position:

1. Quarterback is the single most difficult position to master in the world of team sports. No other position -- not baseball pitcher or soccer goalkeeper or basketball point guard -- requires such a mixture of athletic skills, raw brainpower, functional intelligence and that ineffable something that Hemingway once described as "grace under pressure."

2. It is the single hardest position to evaluate and project in all of professional sports. NFL teams, armed with three or four years of major college game films, hundreds of pages of scouting reports, dozens of hours of workouts in Indianapolis, pro days and individual team workouts, as well as multiple one-on-one personal interviews, still will miss routinely.

Since 1998, 17 quarterbacks have been selected first, second or third overall in the draft. Certainly there are some special names on this list -- Peyton Manning, Eli Manning, Donovan McNabb. As of late, there are some promising picks, as well -- Matt Ryan, Matthew Stafford, Cam Newton. But also on that list of 17 are Ryan Leaf, Tim Couch, Akili Smith, David Carr, Joey Harrington and JaMarcus Russell. What do all these players have in common? The coaches who were there when the players were drafted are no longer employed by those teams.

The franchise quarterback is the Holy Grail of the football business. The search for one can make or break careers. Draft the right quarterback, and everything else you do instantly looks smarter. Pick the wrong one, and you might as well put your house on the market and start updating your résumé. The quest to land the quarterback with the Right Stuff -- along with the fear of missing a chance to draft that quarterback -- gets into the heads of football people. It has humbled men much smarter men than me. Sooner or later, it can force many people in the game to veer from their principles, abandon strategy and skepticism and ... reach.

Consider that from 1999 to 2011, there were 39 quarterbacks drafted in the first round of the draft, but only 16 drafted in the second round. Think about that: By all rights, the distribution from one round to the next should be roughly equal. Even if teams tend to overrate or overvalue quarterbacks, they should overrate them and overvalue them all the way down the line. But that's not what happens. Teams worry nearly as much about passing on a franchise quarterback as they do about drafting a player who turns out to be a bust.

Casserly: Two-round mock draft

Charley Casserly projects the first two rounds of the
2012 NFL Draft, with no quarterbacks coming off the board in Round 2.
More ...

At other positions, there is a rough pecking order based largely on a tangible set of skills that a prospect shows: This wideout has both the speed and the hands to be a first-rounder, while that receiver isn't fast enough to justify a first-round pick. But with quarterbacks, it's different. Too many of the elements are intangible to begin with, or difficult to reliably project from one level to the next. That, combined with the pressure every GM is under to find a franchise quarterback, means that players who have the basic skill set (size, fundamentals and a strong arm) tend to go in the first round, even when there are red flags (ranging from questions about accuracy, makeup, composure or leadership skills) that might compel a team to wait until later in the draft.

In 2008, the Miami Dolphins bypassed QB Matt Ryan, instead taking tackle Jake Long with the first pick of the draft. Long is an outstanding tackle, but four years later, during which time the team has had four different starters at quarterback, the Dolphins are desperately in need of a franchise quarterback. In 2005, the Minnesota Vikings bypassed Aaron Rodgers twice and took wide receiver Troy Williamson and defensive end Erasmus James. Neither Williamson nor James is in the league. And look at the carryover for Minnesota and Miami: The Vikings reached at the quarterback position in last year's draft, taking Christian Ponder at No. 12, while the Dolphins are thinking about doing the same thing in this year's draft, by potentially taking Ryan Tannehill at No. 8.

Need is a terrible negotiator and an even worse evaluator. But the panic to draft someone who might turn out to be great is immense. Which is why, in addition to worrying about whether Tannehill would be a reach at No. 8, the Dolphins are also worrying about if he'll even be around then. Some other, equally desperate team -- Seattle, for instance -- may trade up to take him first.